Starting from amino derivatives of chlorinated aromatic and other model compounds including chlorinated anilines and chlorinated amino biphenyl ethers, various more reactive derivatives including Schiff bases, malonyl diethyl amides, N-hydroxysuccinamide esters (as activated esters), diazoanilines and the like have been prepared. Attempts have been made to prepare defined products on coupling these derivatives to various proteins. Techniques are being developed for the characterization of the conjugates. Relative effectiveness and desirability of various derivatives as antigenic determinants will be assessed.